Hydrocarbon Recovery Process Exploiting Multiple Induced Fractures

ABSTRACT

A method for enhancing production from multiple-fractured underground “tight” formations. Spaced upwardly-extending injection fissures are created along a horizontal injection wellbore, and upwardly-extending collection fissures, alternately spaced with the injection fissures, are created along the horizontal injection wellbore or another adjacent production wellbore. The injection wellbore is supplied with fluid under pressure, which flows into such created fissures and drives reservoir fluids within the formation to the remaining (alternately) spaced adjacent fissures along such wellbore or another parallel adjacent (production) wellbore, thereby allowing reservoir fluids to flow downwardly along such alternately spaced production fissures for collection. In a refinement, production is carried out initially from both the production and injection wellbores, and upon the rate of production of hydrocarbons slowing, production from the injection wellbore is stopped and a fluid is injected therein and thus into the formation via the alternate spaced fissures, thereby re-pressurizing the formation.

CLAIM OF BENEFIT TO PRIORITY

This application claims priority to Canadian Patent Application No.2,820,742, filed Jul. 4, 2013, and to Canadian Patent Application No.2,835,592 filed Nov. 28, 2013, each of which is hereby incorporated byreference in its entirety.

FIELD OF THE INVENTION

The present invention relates to a fluid-drive hydrocarbon recoveryprocess, and more particularly to a fluid drive process which uses fluidinjection in alternating fractures which have been mechanically inducedin a subterranean hydrocarbon-containing formation, with oil and/or gasproduction from the alternating fractures.

BACKGROUND OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART

Multiple fracturing of oil, gas and coal bed methane-bearing formations,where such formations have low permeability (i.e. “tight” reservoirs)are typically necessary to adequately produce hydrocarbons. Various ofsuch methods are now fully commercialized in the prior art as primaryoil and/or gas recovery methods.

Two types of completions for fracturing formations that are currentlyemployed are Packers Plus Energy Services Inc.'s StackFrac™¹ processwhich uses open hole completions, and lined/cemented completions usingtechnology (valves, liners, and the like) supplied by HalliburtonCompany. A horizontal hole is drilled low in the target consolidatedtight-rock hydrocarbon reservoir. In the Halliburton technology, a lineris emplaced in the hole and cemented-in. This assures that there is nodirect communication between the future induced fractures along theoutside of the wellbore. In the Packers Plus technology, the fracturesare accomplished from an open hole—there is no liner. Isolating packerseals (“packers”) situated on injection tubing are actuated down-holewhen in the well, so as to press against the rock itself in order toisolate the zones when conducting fracturing operations and createfissures in the rock, which typically extend upwardly from a horizontalwellbore. After the fracturing operation, the packers are deactivatedand all fractures then produce to the surface, in a process termed“primary production” which terminology is adopted and used herein.Fractures are kept open by the deposit within the fractures of a“proppant” that has been carried into the fractures by the fracturingfluid. Proppants typically consist of sand, metallic or ceramic balls,and/or various chemicals, and provide a relatively high permeabilityflow channel. Formation fluids that flow into the fractures then easilydrain to production tubing within the horizontal hole or wellbore forconveyance to the surface. ¹ StacFrac™ is a registered trademark ofPackers Plus Energy Services Inc. for inter alia the wares of packers,frac-ports, and ball seats.

A major characteristic and benefit of multiple-induced fracturedreservoirs is high initial production rates. Problematically, however,when producing from all fractures simultaneously the production ratesfor such reservoirs typically suffer rapid decline as pressure dropswithin the formation, for reasons as explained below. The multiplefracturing process is expensive, and the overall recovery factors forthese types of formations are typically low, usually achieving recoveryfactors of less than 10% for oil. In order to maintain satisfactoryfield-wide production rates, a vigorous program of capital-intensivedrilling of new multiple-fractured wells is required to compensate forthe high decline rate. The oil production mechanism is by solution gasdrive, and thus there is a rapid decline in the reservoir pressure whichis detrimental to the potential future oil recovery. In this regard, assolution gas comes out of solution with declining pressure within theformation, the viscosity of the remaining oil increases because lightcomponents are removed from the oil. Furthermore, two-phases ofintermingled oil and gas are established, thereby decreasing the oilrelative permeability and further reducing production rates.Consequently the oil flow rate decreases rapidly.

Because hydrocarbons such as shale gas and coal bed methane occur informations of low permeability, recovery of these types of hydrocarbonsparticularly suffer from low recovery factors.

What is needed is a hydrocarbon recovery method for use in conjunctionwith multiple-fractured tight reservoirs, so as to reduce or limit therapid decline in pressure in the formation which typically results, andto limit the number of needed multiply-fractured wells which are neededin “tight” formations to achieve satisfactory percentage recovery fromsuch formations. In particular, an effective fluid-drive process forformations that have and need multiple-induced fractures, that can beapplied as a primary as well as secondary oil recovery method, would beespecially beneficial.

In addition to oil and gas reservoirs, a similar problem occurs in tightcoal-bed methane formations. Methane is adsorbed on the coal, and isrecovered by de-pressuring the formation, which provides only partialrelease of the methane from the coal surface. What is needed is aneffective fluid drive process, ideally using CO₂, which adsorbs muchmore strongly than methane.

US 2013/0048279 as best seen from FIG. 3 thereof, teaches two parallelvertical wells, a second placed a distance from the first, wherein themechanism to produce oil or gas from the formation is located at thesecond well.

US 20120168182 and US 20080087425 both teach inter alia a method forproducing oil and/or gas comprising injecting a miscible enhanced oilrecovery formulation into fractures of a formation for a first timeperiod from a first well; producing oil and/or gas from the fractures,from a second well for the first time period; injecting a miscibleenhanced oil recovery formulation into the fractures for a second timeperiod from the second well; and producing oil and/or gas from thefractures from the first well for the second time period.

US 2006/0289157 teaches a process using gas-assisted gravity drainage,comprising placing one or more horizontal producer wells near the bottomof a pay zone of a subterranean hydrocarbon-bearing reservoir andinjecting a fluid displacer such as CO₂ through one or more verticalwells or horizontal wells. Pre-existing vertical wells may be used toinject the fluid displacer into the reservoir. As the fluid displacer isinjected into the top portion of the reservoir, it forms a gas zone,which displaces oil and water downward towards the horizontal producerwell(s).

US 2006/0180306 teaches a method for recovering crude oil fromsubterranean reservoirs by injecting both water and a second less densefluid to displace the oil, preferably through horizontal wells.

U.S. Pat. No. 8,122,953 teaches inter alia a method of improvingproduction of fluid from a subterranean formation including the step ofpropagating a generally vertical inclusion into the formation, from agenerally horizontal wellbore intersecting the formation.

U.S. Pat. No. 7,441,603 teaches a method for recovery of oil fromimpermeable oil sands, comprising providing vertical fractures usinghorizontal or vertical wells. The same or other wells are used to injectheated pressurized fluids and to return the cooled fluid for reheatingand recycling. The heat transferred to the oil shale gradually maturesthe kerogen to oil and gas as the temperature in the shale is broughtup, and also promotes permeability within the shale in the form of smallfractures sufficient to allow the shale to flow into the well fractures.

U.S. Pat. No. 7,069,990 teaches a process for enhanced oil recovery,comprises providing at least one production well and one injection well;and injecting into the target stratum a slurry formed from sand, viscousliquids or oily sludge, which is delivered at or near formation fracturepressures. Monitoring of bottom hole pressure is carried out, to permitdelivery of the slurried wastes in a series of injection episodes.

U.S. Pat. No. 4,733,726 teaches a method for recovery of oil, whichprovides injection of steam via an injection well into the formation andoil is recovered until there is steam breakthrough at the productionwell. Thereafter, the production well may be shut in or throttled whilecontinuing injection of the steam until the bottom-hole injectionpressure is greater than the vertical pressure created by the overburdenthereby causing the formation to fracture horizontally. A third cycle isinitiated in which oil is recovered from the formation from either theproduction well or the injection well or both until the amount of oilrecovered is unfavorable.

U.S. Pat. No. 4,687,059 teaches injection of water into a subterraneanformation followed by the injection of a polymer solution to drive oiltoward a production well. The polymer solution may thermoelasticallyfracture the formation behind an oil-water bank to increase theinjectivity rate.

U.S. Pat. No. 4,068,717 teaches a oil recovery process by injectingsteam into an injection well penetrating the reservoir sufficiently tofracture the tar sand and provide passage for the steam through the tarsand to a production well piercing a tar sand reservoir.

None of the above prior art, however, teaches anything about creating,in alternating arrangement, injection fissures and producing fissures,to sweep a formation.

What is needed is a hydrocarbon recovery method for use in conjunctionwith multiple-fractured tight reservoirs, so as to reduce or limit therapid decline in pressure in the formation which typically results, andto limit the number of needed multiply-fractured wells which are neededin “tight” formations to achieve satisfactory percentage recovery fromsuch formations. In particular, an effective fluid-drive process forformations that have multiple-induced fractures, that can be applied asa primary as well as secondary oil recovery method, would be especiallybeneficial.

SUMMARY OF THE INVENTION

To improve both production rate and percentage recovery from “tight”formations, and in particular from multiple-fractured wells, in oneembodiment the present invention provides for the creation ofmultiple-induced fractures in a hydrocarbon formation but in particularin two alternating groups, namely injection fractures and producingfractures, which are situated in linear alternating arrangement, whenapproximately ½ of the fractures are used as injection means and theremaining ½ of the fractures used a production means to recoverhydrocarbons. Such method provides an efficient fluid drive toeffectively sweep the formation and drive hydrocarbons into adjacentalternating fissures for subsequent collection. The present method insuch embodiment improves recovery from a formation by providing a fluiddrive via alternate adjacent fissures in the formation, with remainingalternately spaced fissures being used for production.

Specifically, with methods which employ primary oil recovery by solutiongas drive (for example using a vertical injector well for injecting agas into the formation but not using alternating fractures as injectorsand collector channels as described above and below) and particularlywith “tight” formations, as mentioned above typically results in rapiddecline in pressure of the formation, causing a corresponding rapiddecline in production.

Conversely, with the method of the present invention, a high-pressureand high permability injection plane [i.e. the alternatingly spacedfissures located adjacent alternatingly spaced production channels(fissures)] is provided, which then allows a sweep of areas of thereservoir proximate the high permeability injection planes to therebycause a fluid flow vectors within the formation from the highpermeability injection plane in the direction of thealternatingly-spaced production channels (fissures), and consequentimproved sweep of the formation through directed sweep process.

The methods herein are adapted for use in oil and gas containingreservoirs, and are also particularly suited for a particular type ofgas-bearing formation, namely coal-bed methane formations, where thedriving fluid in the method of the present invention using alternatinginjection and recovery channels is CO₂, and which CO₂ driving fluidadvantageously replaces methane on the coal surface and sweeps it to aproximate adjacent production well. Advantageously, where CO₂ is used asa driving fluid in accordance with the method of the present invention,such method advantageously provides for carbon sequestration in the formof subterranean sequestration of the CO₂.

Specifically, in a further aspect of the invention, a well completionmethod is provided in which a plurality of expandable packers are used.

In a first embodiment, vertical fractures are established from ahorizontally-drilled open hole or from a cemented liner therein.Thereafter, a dual tubing (in the form of continuous tubing or segmentedpipe) with spaced-apart isolation packers is run into the open hole orcemented liner. The spaced-apart packers on the tubing are locatedbetween the fractures. Once the packers are expanded against the hole orliner, the fractures will be isolated from each other within the hole orliner. One of the tubings has perforations opposite alternatingfractures, and the other tubing has perforations opposite the remainingfractures. In this way, one tubing string can be employed as aninjection tubing in fluid communication with the alternating injectionfractures, and the other as a production tubing in fluid communicationwith the remaining (alternating) producing fractures.

Accordingly, in said first embodiment of the method of the presentinvention for recovering hydrocarbons from a subterranean formationusing fluid injection in alternating fissures in said formation, usingdual tubing packers, such method comprises the steps of:

-   -   (i) drilling a single injection/production well in said        formation, having a vertical portion and a lower horizontal        portion extending horizontally outwardly from a lower end of        said vertical portion;    -   (ii) fracturing the formation along said horizontal portion of        said injection/production well and creating a plurality of        upwardly-extending fissures extending upwardly from, and        situated along a length of, said horizontal portion;    -   (iii) placing a plurality of packers each having dual tubing        therein along said length of said horizontal portion of said        injection/production well and alternatingly spacing said packers        between said upwardly-extending fissures along said length        thereby partitioning said length into alternatingly-spaced fluid        injection regions and fluid recovery regions, one of said dual        tubing having perforations therein opposite alternatingly-spaced        fissures and the other of said dual tubing having perforations        therein opposite remaining alternatingly-spaced fissures;    -   (iv) injecting a pressurized fluid into one of said dual tubing        and thereby injecting pressurized fluid into said fluid        injection regions and thus into alternatingly-spaced fissures        along said length of said horizontal portion of said        injection/production well; and    -   (v) producing said hydrocarbons which drain into said        alternatingly-spaced fluid recovery regions via other        alternatingly-spaced fissures from said other of said dual        tubing.

The fissures may be created prior to inserting the dual-tubing packersin the wellbore. Alternatively, they may be created after insertingdual-tubing packers into the horizontal portion of theinjection/production well, and pressurized fluid initially supplied toboth of the dual tubings to thereby hydraulically fracture the formationand create uniformly spaced fissures along the wellbore. Thereafter,pressurized fluid is only supplied to ½ of the created fissures (i.e. toevery other fissure along the length of the horizontal portion of thewellbore), and remaining alternately spaced fissures allow hydrocarbonsto drain downwardly into a corresponding fluid recovery region of theinjection/production well, and thereafter be produced to surface by theother of the dual tubing.

One example of dual-tubing packers which may be suitable for use in thisembodiment process of the present invention, at least in a casedwellbore, are dual-tubing packers, namely GT™² Dual-String RetrievablePacker, Product Family Nos. H78509 (Standard Service) and H78510 (NACEService) manufactured by Baker Hughes Corporation, for use in 7 inch(177.8 mm) o.d. (outside diameter) casing, 7⅝ inch (193.7 mm) o.d.casing, or 9 5/5 inch (244.5 mm) o.d. casing. Other suitable dual-tubingpackers for use in this process, both in cased and uncased wellbores,will now occur to persons of skill in the art. ² GT is a trademark ofBaker Hughes Corporation for a dual-tubing packer.

In a most preferred embodiment, a chosen fluid (a gas or liquid) isinjected through the injection tubing. The fluid rises in the formationvia each alternate injection fissures which generally extend verticallyupwardly from horizontal wells. Such injected fluid then sweeps thereservoir fluid laterally in the formation towards the adjacentproducing fissures on each side, whence drainage will be establisheddown into the production tubing for subsequent production of suchformation fluids to surface.

In an alternate embodiment of the invention (the “first variation”),instead of utilizing a dual-tubing within a single wellbore which dualtubing comprises respectively the injection tubing and the productiontubing, such embodiment provides for use of two (2) separately-drilledhorizontal wells, namely an injection well and a production well, eachparallel to the other and in close proximity to the other, wherein oneof such horizontal wells is used for supplying a pressurized fluid toupwardly-extending fissures which have been created along a horizontallength of a such injection well, and the other well is used as theproduction well for fractures that have been created along suchremaining horizontal well that are alternately spaced and areinterdigitated between alternate fissures created along the injectionwell. Specifically, upwardly extending substantially vertical injectionfractures/fissures are established along the horizontal portion of theinjection well. Vertical fractures/fissures are also likewiseestablished along the horizontal portion of the production well, butthese fractures are laterally offset from the fractures established formthe injection well. In other words, scanning horizontally across theformation, the intercepted fractures are alternatively fluid-injectionfractures and producing fractures. Production occurs by a fluid beinginjected via the injection well into fissures along such horizontal(injection) well, and reservoir fluids are then driven into alternatelyspaced fissures previously created along the horizontal production well,which reservoir fluids then flow downwardly and are collected inproduction tubing within the production well. Advantageously in suchmanner the injected fluid is injected in the formation where it may mosteasily and directly carry out its intended purpose, namely to bestdirect reservoir fluids into alternately spaced adjacent fissures withinthe formation, which thereby drain downwardly. Such reservoir fluids,after draining downwardly in said alternately-spaced fissures, arerecovered by the production tubing in the production well and producedto surface.

The lateral separation distance between various adjacent sequentialinjection and production fractures/fissures may vary, or may beconstant, and will be selected based on standard reservoir engineeringanalysis of the properties of the formation obtained through variousknown and widely used well logging techniques, and will depend onreservoir parameters along the wells, such as but not limited to, matrixpermeability, matrix fracture pressure, produced hydrocarbon mobility,injectivity of the injection fluid, and desired injection and productionrates. Numerical simulation using software such as licensed by theComputer Modelling Group of Calgary, Alberta, Canada can assist in theselection of injection fluid and determination of lateral offset of theindividual injection and production fractures relative to each other.

Accordingly, in a broad alternate aspect, the process of the presentinvention comprises a process for recovering hydrocarbon from asubterranean formation utilizing propped hydraulic fractures, comprisingthe steps of:

-   -   (i) drilling an injection well having a vertical portion and a        horizontal portion extending horizontally outwardly from a lower        end of said vertical portion thereof;    -   (ii) drilling a production well having a vertical portion and a        horizontal portion extending outwardly from a lower end of said        vertical portion thereof, wherein said horizontal portion of        said production well is situated parallel to said horizontal        portion of said injection well;    -   (iii) creating upwardly-extending fissures in the formation        along each of said horizontal portions of said production well        and injection well by injecting a pressurized fluid into each of        said production well and injection well, at a plurality of        discrete locations along a length of each of said horizontal        portion of each of said production well and injection well,        wherein said discrete locations in said production well        substantially correspond in number to said discrete locations in        said injection well and wherein said discrete locations and each        of said respective fissures extending upwardly along said        injection well are in alternating linear spacing and        substantially mutually adjacent relation with corresponding        respective fissures extending upwardly along said horizontal        portion of said production well;    -   (iv) said pressurized fluid containing a proppant, or        alternatively after step (ii) above injecting a proppant under        pressure into said created fissures to render said fissures in a        propped condition; and    -   (v) continuing to inject said pressurized fluid, or injecting        another fluid, into said injection well and thereby into said        fissures above said injection well and thence into said        formation thereby pressurizing said formation and causing said        hydrocarbons within said formation to be driven into said        fissures above said production well, and to drain downwardly        therein into said horizontal portion of said production well;        and    -   (vi) producing said hydrocarbons which collect in said        horizontal portion of said production well to surface.

In a similar embodiment of the invention, the invention comprises aprocess for recovering hydrocarbons from a subterranean formationutilizing propped hydraulic fractures comprising the steps of:

-   -   (i) drilling an injection well, having a vertical portion and a        horizontal portion extending horizontally outwardly from a lower        end of said vertical portion along a lower portion of the        formation;    -   (ii) drilling a production well having a vertical portion and a        horizontal portion extending outwardly from a lower end of said        vertical portion, wherein said horizontal portion of said        production well is situated proximate to, parallel with, and        spaced apart from, said horizontal portion of said injection        well;    -   (iii) fracturing the formation along each of said production        well and injection well and creating a plurality of        upwardly-extending fissures extending upwardly from, and        situated along a length of, said horizontal portion of each of        said injection well and said production well, said        upwardly-extending fissures created along said injection well        mutually alternating along said horizontal length thereof with        upwardly-extending fractures situated along said production        well;    -   (iv) utilizing injection tubing, having therealong a plurality        of spaced-apart packer seals within a length of said horizontal        portion of said injection well, said injection tubing further        having apertures or apertures which may be opened intermediate        pairs of said spaced-apart packer seals situated at locations at        which said upwardly-extending fractures are located along said        injection well, and injecting a pressurized fluid into said        injection tubing and into said fissures extending along said        horizontal portion of said injection well;    -   (v) utilizing production tubing, having therealong a plurality        of spaced-apart packer seals similarly spaced apart as per said        packer seals along said injection tubing, said production tubing        further having apertures, or apertures which may be opened,        intermediate pairs of said spaced-apart packer seals, along a        length of said horizontal portion of said production well,        wherein said apertures in said production tubing are positioned        in alternating and non-lateral alignment with said apertures        located in said injection tubing, and collecting from said        formation hydrocarbons in said production tubing which flow into        said fissures and which drain downwardly into said production        tubing via said apertures therein; and    -   (vi) producing the hydrocarbons which collect in said production        tubing to surface.

The above method may be used wherein the injection well is an open hole,or one where a liner is used. Where a liner is used, packer seals neednot be used, but the hole must be lined and cemented, otherwise thefirst wellbore will fill with injection fluid when the second wellboreis fractured. Specifically, where a lined well(s) are desired and nopacker seals are therefore needed, the above method is further modified,wherein:

-   -   (a) step (i) above further comprises the step of inserting and        cementing a liner in the injection well;    -   (b) step (ii) further comprises the step of inserting and        cementing a liner in said production well;    -   (c) adding a step, after step (ii), of creating perforations in        said liner and cement in each of said horizontal portions of        said production and injection wells, at a plurality of discrete        allocations therealong, wherein said discrete locations in said        production well are approximately equal in number but linearly        alternating with said corresponding perforations created in said        cemented liner in said injection well.

Alternatively to the above methods, a two-step process may beundertaken. Specifically, after creating the fractures along each of theproduction well and injection wells in the manner described above, boththe production well and injection wells are initially put on productionas is traditionally done, producing reservoir fluids which draindownwardly from all fissures (primary production). Thereafter, namely ata point in time when production rates typically drop off and start tobecome uneconomical as typically occurs in multiple-fractured “tight”formations, production from the injection well is stopped, and a fluidis then injected into alternate fissures via tubing within the injectionwell, to thereby begin the fluid drive process described above, withfluid production continuing from remaining alternately spaced fissuresin the formation. In such manner the production rate can be restored tosimilar earlier levels, and the overall recovery from the formationincreased.

Accordingly, in accordance with the above two-step process, in oneembodiment thereof such process comprises a process for recoveringhydrocarbons from a subterranean formation utilizing propped hydraulicfractures comprising the steps of:

-   -   (i) drilling an injection well, having a vertical portion and a        horizontal portion extending horizontally outwardly from a lower        end of said vertical portion;    -   (ii) inserting tubing, having therealong a plurality of        spaced-apart packer seals, within a length of said horizontal        portion of said injection well, said tubing further having        apertures or apertures which may be opened intermediate pairs of        said spaced-apart packer seals;    -   (iii) drilling a production well proximate said injection well,        having a vertical portion and a horizontal portion extending        outwardly from a lower end of said vertical portion, wherein        said horizontal portion of said production well is situated        proximate to, parallel with, and spaced apart from, said        horizontal portion of said injection well;    -   (iv) inserting tubing, having therealong a plurality of        spaced-apart packer seals similarly spaced apart as per said        packer seals in said injection well, said tubing further having        apertures, or apertures which may be opened, at locations        intermediate pairs of said spaced-apart packer seals, along a        length of said horizontal portion of said production well,        wherein said apertures in said tubing in said production well        are positioned in non-lateral alignment with said apertures in        said injection well;    -   (v) setting, if necessary, said packer seals in each of said        respective horizontal portions of said injection well and said        production well so as to prevent flow of fluid along an annular        passage intermediate said tubing and said production well and        injection well, respectively;    -   (vi) injecting into said injection well, a fluid under pressure        and causing said fluid to flow into said formation via said        apertures in said tubing therein, so as to create upwardly        extending fissures at each of said apertures along said        injection well;    -   (vi) injecting into said production well, a fluid under pressure        and causing said fluid to flow into said formation via said        apertures in said tubing therein, so as to create upwardly        extending fissures at each of said apertures along said        production well;    -   (vii) after step (vi) collecting, via said tubing in said        horizontal portion of said production well and said horizontal        portion of said injection well, said hydrocarbons which flow        into said fissures and which drain downwardly into said tubing        in said production well and said injection well;    -   (ix) after a period of time and when production from said        production well and said injection well decreases to an        unsatisfactory rate, injecting a fluid into said injection well        and into said upwardly-extending fissures along said injection        well; and    -   (x) continuing to collect, via said horizontal portion of said        production well, said hydrocarbons which flow into said fissures        above said production well and which drains downwardly into said        tubing in said production well.

In a variation of the present invention (the “second variation”), only asingle (injection/production) well is drilled, and pairs of adjacentfissures are used as an injection fissure and an adjacent productionfissure, respectively, with fluid in the injection fissure forcinghydrocarbons in the formation to the production fissure. Thereafter,either the production fissure is converted into an injection fissure byinjection of fluids therein, or the injection fissure is converted intoa production fissure, and a “sweeping” method is used as set out below.

Specifically, in a first embodiment of such second variation, afterproduction for a time from a production fissure, production ofhydrocarbons from said production fissure is ceased, and such fissuresubsequently used, in the manner described below, as an injectionfissure, and fluids injected therein drive hydrocarbons to another(other) adjacent production fissure(s).

Accordingly, in such first embodiment of this second variation, suchmethod comprises a process for recovering hydrocarbons from asubterranean formation utilizing propped hydraulic fractures comprisingthe steps of:

-   -   (i) drilling an injection/production well, having a vertical        portion and a horizontal portion extending horizontally        outwardly from a lower end of said vertical portion, said        horizontal portion having a heel portion proximate said vertical        portion, and a toe portion proximate a distal end of said        horizontal portion;    -   (ii) creating upwardly-extending fissures in the formation along        said horizontal portion by injecting a pressurized fluid at a        plurality of discrete spaced locations along a length of said        horizontal portion;    -   (iv) said pressurized fluid containing a proppant, or        alternatively after step (ii) above injecting a proppant under        pressure into said created fissures to render said fissures in a        propped condition; and    -   (v) positioning injection tubing into said wellbore, said        injection tubing having an actuatable packer member proximate a        distal end of said tubing adapted when actuated to create a seal        between said tubing and said wellbore, and situating such packer        member and injection tubing within said wellbore on a heel side        of a most distal upwardly-extending fissure;    -   (vi) injecting said pressurized fluid, or injecting another        fluid, into said injection tubing so as to cause said fluid to        flow into said most distal upwardly-extending fracture, and        producing oil to surface which flows into an annular area in        said wellbore via a penultimate fissure adjacent said most        distal upwardly-extending fissure;    -   (vii) deactivating said packer member and moving said packer        member and injection tubing toward said vertical portion, and        re-instituting injection of said fluid so as to inject said        fluid into said penultimate upwardly-extending fissure, and        producing oil which flows into said annular area via a fissure        adjacent said penultimate fissure on a heel side of said        penultimate fissure.

Of course, rather than commencing at the toe portion and initiallyinjecting fluid into the most distal upwardly extending fracture,commencing at the heel, such method may be similarly employed by insteadinitially injecting through the most proximal upwardly-extending fissurewhich is proximate the heel, and thereafter progressing in the mannerdescribed above toward the toe.

Accordingly, in such alternate process, such comprises the steps of:

-   -   (i) drilling an injection/production well, having a vertical        portion and a horizontal portion extending horizontally        outwardly from a lower end of said vertical portion, said        horizontal portion having a heel portion proximate said vertical        portion, and a toe portion proximate a distal end of said        horizontal portion;    -   (ii) creating upwardly-extending fissures in the formation along        said horizontal portion by injecting a pressurized fluid at a        plurality of discrete spaced locations along a length of said        horizontal portion;    -   (iv) said pressurized fluid containing a proppant, or        alternatively after step (ii) above injecting a proppant under        pressure into said created fissures to render said fissures in a        propped condition; and    -   (v) positioning injection tubing into said wellbore, said        injection tubing having an actuatable packer member proximate a        distal end of said tubing adapted when actuated to create a seal        between said tubing and said wellbore, and situating said packer        member and injection tubing within said wellbore on a toe side        of a most proximal upwardly-extending fissure;    -   (vi) actuating said packer member and injecting said pressurized        fluid, or injecting another fluid, into said injection tubing so        as to cause said fluid to flow into one or more of remaining        upwardly-extending fissures, and producing oil to surface which        flows into an annular area in said wellbore via said most        proximal fissure;    -   (vii) de-actuating said packer member and moving said packer        member and injection tubing toward said toe portion,        re-activating said packer member and re-instituting injection of        said fluid, and injecting said fluid into remaining        upwardly-extending fissures, and producing oil which flows into        said annular area via said most proximal fissure and a further        adjacent penultimate fissure.

In a second embodiment of the above second variation, after injection offluid for a time into an injection fissure has occurred, injection offluids into said injection fissure is ceased, and such fissuresubsequently used, in the manner described below, as a productionfissure which has hydrocarbons driven to such converted fissure viafluid injected into the formation via another (other) injectionfissures.

Accordingly, in such second embodiment of this second variation, suchmethod comprises a process for recovering hydrocarbons from asubterranean formation utilizing propped hydraulic fractures which areemployed as production channels and subsequently as injection channels,comprising the steps of:

-   -   (i) drilling an injection/production well, having a vertical        portion and a horizontal portion extending horizontally        outwardly from a lower end of said vertical portion, said        horizontal portion having a heel portion proximate said vertical        portion, and a toe portion proximate a distal end thereof;    -   (ii) creating upwardly-extending fissures in the formation along        said horizontal portion by injecting a pressurized fluid at a        plurality of discrete spaced locations along a length of said        horizontal portion;    -   (iv) said pressurized fluid containing a proppant, or        alternatively after step (ii) above injecting a proppant under        pressure into said created fissures to render said fissures in a        propped condition; and    -   (v) positioning production tubing into said wellbore, said        production tubing having an opening and an actuatable packer        member thereon proximate a distal end thereof adapted when        actuated to create a seal between said tubing and said wellbore,        and situating said packer member proximate a toe region of said        wellbore on a heel side of a most distal upwardly-extending        fissure;    -   (vi) actuating said packer member and injecting said pressurized        fluid, or injecting another fluid, into an annular area        intermediate said production tubing and said wellbore and        thereby injecting said fluid into a penultimate fissure adjacent        said most distal upwardly-extending fracture, and producing        hydrocarbons via said production tubing which drain into said        wellbore via said most distal upwardly-extending fissure and        which thereafter flow into said production tubing via said        opening therein;    -   (vii) deactuating said packer member and moving said packer        member and production tubing toward said heel portion,        re-actuating said packer member and re-instituting injection of        said fluid into said annular area so as to inject said fluid        into an upwardly-extending adjacent fissure on a heel side of        said penultimate fissure, and producing oil which flows into        said production tubing via said penultimate fissure.

Again, rather than commencing at the toe portion and initially producingfrom the most distal upwardly extending fracture, such method may bemodified to commence at the heel, such method may be similarly employedby instead initially injecting through the most proximalupwardly-extending fissure which is proximate the heel, and thereafterprogressing in the manner described above toward the toe.

In such aspect of the second variation, such method comprises the stepsof:

-   -   (i) drilling an injection/production well, having a vertical        portion and a horizontal portion extending horizontally        outwardly from a lower end of said vertical portion, said        horizontal portion having a heel portion proximate said vertical        portion, and a toe portion proximate a distal end thereof;    -   (ii) creating upwardly-extending fissures in the formation along        said horizontal portion by injecting a pressurized fluid at a        plurality of discrete spaced locations along a length of said        horizontal portion;    -   (iv) said pressurized fluid containing a proppant, or        alternatively after step (ii) above injecting a proppant under        pressure into said created fissures to render said fissures in a        propped condition; and    -   (v) positioning production tubing in said wellbore, said        production tubing having an opening and an actuatable packer        member thereon proximate a distal end thereof adapted when        actuated to create a seal between said tubing and said wellbore,        and situating said packer member proximate a heel portion of        said wellbore on a toe side of a most proximal        upwardly-extending fissure;    -   (vi) actuating said packer member and injecting said pressurized        fluid, or injecting another fluid, into an annular area        intermediate said production tubing and said wellbore and        thereby injecting said fluid into said most proximal fissure        adjacent, and producing hydrocarbons via said production tubing        which drain into said wellbore via said remaining        upwardly-extending fissure and which thereafter flow into said        production tubing via said opening therein;    -   (vii) deactuating said packer member and moving said packer        member and production tubing toward said toe portion,        re-actuating said packer member and re-instituting injection of        said fluid into said annular area so as to inject said fluid        into a penultimate upwardly-extending fissure on a heel side of        said most proximal fissure, and producing oil which flows into        said production tubing via an adjacent remaining fissure.

In all embodiments of the method of the present invention thehydrocarbon recovered is preferably oil or gas.

In a refinement of the above methods, the recovered hydrocarbon ismethane, and the injected fluid is CO₂.

In a further refinement, the injected fluid is miscible or immiscible inthe hydrocarbon contained within the formation which is being recovered.

In a still further embodiment, the injected fluid is a gas, such as CO₂or water vapour, or alternatively is a liquid such as water.

In a further embodiment, the injected fluid contains oxygen, for use inan in-situ combustion process.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side cross-sectional view of one embodiment (the “firstvariation”) of the process of the present invention for fracturing andextracting oil from an underground formation, showing fluid flow througheach of the two sets of fissures, namely alternately spaced injectionfissures and production fissures;

FIG. 2 is a perspective view of the embodiment of the invention shown inFIG. 1;

FIG. 3 is a partial cross-sectional view along arrows “A-A” of FIG. 2;

FIGS. 4A-4C show another embodiment of the process of the presentinvention, commencing with injection of fluid via the fracture at thedistal end of the horizontal wellbore and producing from the adjacentfracture and, to a lesser extent, other fractures more proximate theproximal end of the horizontal wellbore (FIG. 4A), and subsequentlymoving a plug member toward a proximal (heel) end of the wellborethereby converting fractures used for production into injection wells(FIGS. 4B, 4C);

FIGS. 5A-5C show another embodiment of the process of the presentinvention similar to the embodiment shown in FIGS. 4A-4C commencing withinjection of fluid via the penultimate distal fracture along thehorizontal wellbore and producing from the most distal fracture, andsubsequently moving a plug member toward the proximal (heel) end of thewellbore and subsequently thereby converting injection fractures intoproducing fractures (FIGS. 5B, 5C);

FIG. 6 is a sectional schematic view of a typical packer element whichis used as part of the present process to, upon actuation after beinginserted in a production well or injection well, create a seal tothereby isolate individual locations along the respective productionwell and injection well, to allow fracturing of the formation atdiscrete intervals along horizontal portions of the injection andproduction wells;

FIG. 7 is a cross-sectional view of a typical pressure-actuated slidingsleeve which is used as part of the present process, particularly inopen hole configurations, wherein the sliding sleeve is shown in theclosed position for insertion into an open hole, and may thereafterthrough hydraulic fluid pressure applied thereto, cause an aperturetherein to open;

FIG. 8 is a similar sectional view of the pressure-actuated slidingsleeve of FIG. 7, wherein the sliding sleeve is shown in the positionwhere the aperture is opened;

FIG. 9 is a graph showing oil production rate in m3/day (y axis) vs.time (days) (x axis) for various configurations allowing comparison ofthe method of the present invention shown in FIGS. 1-3 compared with theprior art method of producing from all fissures, wherein curve (a) isproduction without injection of driving fluid, curve (b) is the oil rateusing gas fluid drive (methane), curve (c) is the oil rate with 2-yearsof primary oil production followed by gas injection (methane), and curve(d) is the oil rate where water is used as the injection fluid intoalternately spaced fissures;

FIG. 10 is a graph showing oil recovery factor (y axis) as a percentageof original oil in place (% OOIP) vs. time (days) (x axis) for variousconfigurations allowing comparison of the method of the presentinvention shown in FIGS. 1-3 compared with the prior art method ofproducing from all fissures, where line (i) is the % OOIP using primaryproduction methods (ie from the injection and production wells), line(ii) is the % OOIP using gas drive fluid injection in the injectionwell, line (iii) is the % OOIP with 2-years of primary oil productionfollowed by gas injection, and line (iv) is the % OOIP using waterinjection;

FIG. 11 is a depiction of, respectively, two versions of a dual-tubingpacker, which can coupled together be used in the method of the presentinvention in a single well for allowing fluid injection in alternatelyspaced vertical fissures and recovery of oil from alternately spacedfissures in the formation;

FIG. 12 is a schematic rendition of the method of the present inventionusing dual-tubing packers of the type described herein and shown in FIG.11, and a single well for allowing fluid injection in alternately spacedvertical fissures and recovery of oil from alternately spaced fissuresin the formation;

FIG. 13 is an enlarged schematic rendition of a formation, using onlyprimary oil recovery, whereby collection is from all fissures/fractures;and

FIG. 14 is a similar enlarged schematic rendition of section of aformation intermediate two alternatingly spaced fractures in accordancewith one method of the present invention, wherein the first series offractures is used as a high pressure injection plane so ast o producehigh pressure in the region of injection fractures, and the mostproximate alternatingly spaced fractures are used as a low pressure andhigh permeability production plane.

DETAILED DESCRIPTION OF SOME PREFERRED EMBODIMENTS

With reference to FIGS. 1, 2, & 3, item 20 indicates a depiction of onemethod (“the first variation”) of the present invention for recoveringhydrocarbons from a multiple-fractured a “tight” subterranean formation6 possessing a hydrocarbon-containing reservoir, above which istypically a layer of cap rock 1 and below which is typically a layer ofbottom rock 2.

Thus in such first variation two wells are drilled into reservoir 6,namely an injection well 12 having a vertical portion 32 and ahorizontal portion 44, and a production well 8 similarly having acorresponding vertical portion 33 and a horizontal portion 45.

The horizontal portion 45 of the production well 8 is drilled parallelto, and proximate, the horizontal portion 44 of injection well 12, asshown in FIGS. 1 & 2. Horizontal portion 45 may be drilled level with,or alternatively spaced vertically above or below (see FIG. 3, forexample) horizontal portion 44.

A liner (not shown) may be inserted into one or both of such wells 8,12, and cemented in place. If a liner is used in production well 8 andinjection well 12, the horizontal portion 45 of production well 8 isperforated at discrete locations 38 therealong using procedures wellknown to persons of skill in the art, and the horizontal portion 44 ofinjection well 12 is similarly perforated at (mutually alternating)discrete locations 37, to allow flow of pressurized fluid into theformation 6, and collection of hydrocarbons from the formation 6, asmore fully explained below.

Fracturing of the formation 6 is conducted by injecting pressurizedfluid at discrete locations 37, 38 along the length respectively ofhorizontal portions 44, 45 so as to create fissures 5 a, 5 b withinformation 6 extending respectively upwardly from such discrete locations37,38 along horizontal portions 44, 45 respectively.

Importantly, discrete locations 37 along length of horizontal portion 44of injection well 12 are in mutually alternating spaced relationship tothose discrete locations 38 extending linearly along the length of thehorizontal portion 45 of production wellbore 8, so as to thereby allow,when pressurized fluid in injected at such discrete locations 37,38,respectively upwardly-extending fissures 5 b, 5 a to be created information 6, in mutually alternating substantially linear relationship,as shown in FIGS. 1 & 2.

The fracturing may be conducted by inserting tubing 55, 56 in each ofrespective horizontal portions 44, 45, wherein each of tubing lines 55,56 (which may be continuous tubing or jointed pipe string) possess anumber of spaced-apart packer seals 9 along the length thereof. Packerseals 9, one example of which is depicted in FIG. 6, are well known inthe art, and are commercially available from various well-knowndown-hole tool companies such as Packers Plus Inc. (particularly forun-lined wellbores) and by Halliburton company (particularly for linedand cemented wellbores). Packer seals 9, in one embodiment thereof asshown in FIG. 6, possess a hydraulically-actuated piston 18. Whenpressurized fluid is supplied to tubing lines 55, 56 to which suchpacker seals 9 are operatively coupled, such pressurized oil flowsthrough ports 22 where it acts on dual pistons 18 which then laterallycompress and causes radial expansion outwardly of a resilient material17 (see FIG. 6), which resilient material 17 then creates a seal betweenhorizontal wellbore 44, 45 (or tubing liner, as the case may be) andtubing 55, 56 respectively.

With reference to FIGS. 1-3, tubing 55, 56 may be hung, respectively, invertical portions 32, 33 of injection and production wells 12, 8 bytubing hangers 30, 25, respectively, as shown in FIG. 1.

When elongate tubing 55, 56 is used, hydraulically-actuated sleeves 15may be interposed intermediate pairs of packer seals 9. Such sleeves 15,one example of which is shown in detailed view in FIG. 7 (closedposition) and FIG. 8 (open position), each possess an aperture 21, whichupon application of hydraulic pressure to interior of sleeve 15 andrelease of locking ring 42, causes such aperture 21 to be opened toallow egress of pressurized fluid from within tubing 55, 56 to flow intothe formation 6 so as to cause fracturing and thus create fissures 5 a,5 b. Such sleeves 15 may, along with tubing 55, 56, be inserted, when ina closed position as shown in FIG. 7, down into respective horizontalportions 44,45, and when in a desired location 37, 38, be actuated viahydraulic pressure to cause sleeves 15 to expose apertures 21 (see FIG.8), thereby allowing such pressurized hydraulic fluid to be exposed tothe formation, thereby creating fissures 5 a, 5 b. Hydraulicallyactuated sleeves 15 are likewise commercially available, one such sleevebeing available from Packers Plus Inc. of Calgary, Alberta.

Alternatively, creation of fissures 5 a, 5 b along horizontal portions44, 45 respectively may be conducted by the traditional, if not somewhatoutdated and more time consuming procedure of the so-called “plug andperf” procedure. In such procedure, a single pair of pressure-actuatedpacker seals 9 are provided at a distal end of tubing, such tubinghaving a single aperture 21 intermediate said pair of packer seals 9.The pair of packer seals 9 are actuated and thereby deployed to create aseal at various discrete locations 37,38 along each of horizontalportions 44, 45 by pushing (or pulling) such packer seals 9 and tubingalong the length of each of said horizontal portions 44, 45, and at suchtime pausing to supply hydraulic fluid at each of the discrete locations37,38 so as to create fissures 5 a, 5 b at each of such locations 37, 38respectively therealong. Again, the discrete locations 37 in horizontalportion 44 of injection well 12 are in mutually alternating spacedarrangement to the discrete locations 38 in horizontal portion 45 ofproduction well 8 in accordance with the method of the presentinvention, to thereby provide for the injection of pressurized fluidintermediate and closely proximate, adjacent fissures 5 b as shown inFIGS. 1 & 2, so as to best be able to re-pressurize such “tight”formation 6 at locations where such repressurization is most useful.

Fluid which is injected for the purpose of creating fractures/fissures 5a, 5 b as described above may contain a proppant to maintain thefissures 5 a, 5 b in an expanded position. Alternatively, after creationof such fissures 5 a, 5 b, a second fluid containing such proppant maythereafter be injected down-hole via tubing 55, 56 to maintain thecreated fissures in an “open” position.

The same fluid, or even a third fluid, may be used as the driving fluidwhen carrying out the method of the present invention for sweeping theformation.

Upon creating of fissures 5 a, 5 b in formation 6, should no tubing suchas tubing 55, 56 with associated packer seals 9 and sliding sleeves 15have been previously used in fracturing and remain in place inhorizontal portions 44, 45, such a tubing string 55, 56, and associatedpacker seals 9 and associated sleeves 15 are inserted in each ofhorizontal portions 44, 45. Packer seals 9 are then actuated, andadjacent fissures 5 a, 5 b thereby isolated from each other. Aninjection fluid is injected through the injection tubing 55. Theinjectant fills the vertical fractures 5 a that are above the injectiontubing 55, by travelling into fissures 5 a via perforations in the wellliner (if a well liner is used) at discrete locations 37 alonghorizontal portion 44, and rise in fissures 5 a whereafter suchinjectant fluid is forced into the formation 6 and flows laterallytowards the adjacent fissures 5 b that are themselves in communicationwith the production tubing 56. Reservoir fluids that drain into theproduction tubing 56 are lifted to the surface, typically by pumping.The injectant fluid may be, but is not limited to, the followingsubstances, namely: produced gas, flue gas and others; oxygen-containinggases such as air, oxygen or mixtures thereof in an in situ combustionprocess; liquids that may or may not be soluble in the reservoirhydrocarbon, such as water, steam or natural gas liquids.

In a preferred embodiment, this process of enhanced hydrocarbon recoveryusing hydraulically-induced and propped reservoir fractures 5 a 5 b isconducted in the native reservoir without de-pressuring in order tomaintain the maximum hydrocarbon mobility. However, there will beoccasions when the well operator will desire to conduct traditionalprimary petroleum production first, or where the reservoir has alreadybeen de-pressured, but nevertheless the present invention can still beutilized beneficially.

Due to the increased pressure in the formation 6 resulting frominjection of fluid into the formation via fissures 5 b, hydrocarbons andreservoir fluid present in formation 6 are encouraged and driven towardfissures 5 a interposed between fissures 5 b, as shown in FIGS. 2 & 3,and thereafter drain downwardly to be collected by production tubing 56,and thereafter are pumped to surface.

In a refinement of the above method, immediately upon creation of thefissures 5 a, 5 b along each of horizontal portions 44, 45 respectively,no injection of fluid is commenced in the injection well 12, and insteadall fissures 5 a, 5 b are allowed to receive hydrocarbon fluids from theformation 6. Both the injection well 12 and the production well 8 usedto collect and produce hydrocarbons to surface. After a period of timewherein ambient pressure in formation 6 has become reduced due towithdrawal of hydrocarbons from formation 6, and production thereofreduced to an unacceptably low production rate, injection well 12 isconverted from a production well to an injection well, by pressurizingfluid being injected into horizontal portion 44 and thus into fissures 5a. Such procedure then creates zones of higher pressure substantiallyintermediate fissures 5 b, thus “driving” remaining hydrocarbons information 6 into fissures 5 b, for subsequent collection by productiontubing 56, and for production to surface.

In the second variation of the method of the present invention, a firstembodiment thereof being shown in FIGS. 4A-4C, only a singleinjection/production well 90 is drilled, having a vertical portion 91,and a horizontal portion 92 extending outwardly from a lower end of thevertical portion 91. A heel portion 99 is present at the base of thevertical portion 91, namely at the most proximal end of the horizontalportion 92, and a toe portion 100 is present at the opposite, mostdistal end of the horizontal portion 92.

Upwardly-extending fissures, shown as 5 a, and 5 b, 5 b′, 5 b″, 5 b′″, 5b ^(iv) and 5 ^(v) in FIG. 4A, are created along the length ofhorizontal portion 92 by injecting a pressurized fluid at a plurality ofdiscrete spaced locations along a length of said horizontal portion 92.The pressurized fluid contains a proppant, or alternatively a proppantis thereafter injected under pressure into said created such fissuresand to render said fissures in a propped condition. Thereafter,injection tubing 55 is placed in horizontal portion 92 of well 90.Injection tubing 55 as an actuatable packer member 93, such as shown inFIG. 6, situated proximate a distal end of said tubing 55. Actuatablepacker 93 is adapted, when hydraulically actuated via pressure in tubing55, to create a seal between said tubing 55 and said horizontal portion92.

In one embodiment of the process shown successively in FIGS. 4A-4C,packer 93 and injection tubing 55 is initially situated on a heel sideof a most distal upwardly-extending fissure 5 a as shown in FIG. 4A.Pressurized fluid 96 is injected into said injection tubing 55 so as tocause said fluid to flow into said most distal upwardly-extendingfracture 5 a, and producing oil to surface which flows into an annulararea in said wellbore via a penultimate fissure 5 b adjacent said mostdistal upwardly-extending fissure 5 a.

Thereafter, packer member 93 is deactivated, and tubing 55 and packermember 93 are moved toward the heel 99, as shown in FIG. 4B. Packermember 93 is re-actuated so as to create a seal between injection tubing55 and wellbore 90. Injection of said fluid 96 is re-commenced so as toinject said fluid 96 into said penultimate upwardly-extending fissure 5a′, and producing oil which flows into said annular area via a fissure 5b′ adjacent said penultimate fissure 5 a′ on a heel side of saidpenultimate fissure 5 a.

Such process is further repeated, as shown in FIG. 4C, and thereafter,each time progressively converting successive production fissures 5 b″,5 b′″, 5 b ^(iv) and 5 ^(v) to respective production fissures 5 a′, 5a″, etc. until reaching the heel portion 99 of horizontal portion 92,when hydrocarbons in such formation 6 will have then been substantiallyrecovered.

Of course, the reverse of such process may also be conducted, to achievesubstantially the same result, progressively driving and recovering fromformation 6, from a heel 99 to toe 100, and in effect reversing thesequence, as shown progressively in FIGS. 4C-4A.

In such embodiment, the fissures 5 a and 5 b, 5 b′, 5 b″, 5 b′″, 5 b^(iv) and 5 ^(v) are created as before, with fissure 5 a being thefissure most proximate the heel portion 99 (ie situated at the proximalend of horizontal portion 92), and fissures 5 b, 5 b′, 5 b″, 5 b′″, 5 b^(iv) and 5 ^(v) extending respectively toward the toe 100. In suchembodiment, when injection tubing 55 is positioned, along with actuablepacker 93 in horizontal portion 92, such is positioned on a toe side ofmost proximal upwardly-extending fissure 5 a. Packer 93 is actuated³,and pressurized fluid 96 is injected into tubing 55 and thereby causedflow into fissure 5 b, and possibly in addition remaining fissures 5 b′,5 b″, 5 b′″, 5 b ^(iv) and 5 ^(v). Hydrocarbons which flows into anannular area in said wellbore intermediate tubing 55 and wellbore 90 viasaid most proximal fissure 5 a are produced to surface. Thereafter,packer member 93 is deactuated, and moved with said injection tubingtoward toe portion 100, where packer member 93 is re-actuated. Fluid 96is again injected into remaining upwardly-extending fissures 5 b″, 5b′″, 5 b ^(iv) and 5 ^(v), and hydrocarbons which flow into said annulararea via said most proximal fissure 5 a and into a further adjacentpenultimate fissure 5 a′, are produced to surface. Such process isfurther repeated, and thereafter, each time progressively convertingsuccessive production fissures 5 b″, 5 b′″, 5 b ^(iv) and 5 ^(v) torespective production fissures 5 a′, 5 a″, etc. until reaching the toeportion 100 of horizontal portion 92, when hydrocarbons in suchformation 6 will have then been substantially recovered. ³ In thisembodiment packer 93 is not actuated by pressure within tubing 55 butrather actuated via other means well known to persons of skill in theart, such as by ball-drop methods, which are not needed to be discussedherein

In a second embodiment of the second variation of the process of thepresent invention shown in FIGS. 5A-5C, again only a singleinjection/production well 90 is drilled, and upwardly extending fissures5 a and 5 b are created along the length of horizontal portion 92, asshown in FIG. 5A, as per the manner described above. Production tubing55 having an open end 94 and an actuatable packer 93 thereon is situatedin horizontal portion 92, with packer member 93 situated proximate a toeportion 100, on a heel side of a most distal upwardly-extending fissure5 b, as shown in FIG. 5A. Packer member 93 is actuated to create a sealbetween tubing 55 and wellbore 90, and fluid 96 is injected into anannular area intermediate said production tubing 55 and said wellbore 90and thereby into a penultimate fissure 5 a adjacent said most distalupwardly-extending fissure 5 b, as shown in FIG. 5A. Hydrocarbons 95which drain into said horizontal portion 92 via said most distalupwardly-extending fissure 5 b and which thereafter flow into saidproduction tubing via said opening 94 therein, are produced to surface.After production slows, packer member 93 is de-actuated, and moved alongwith production tubing 55 towards heel portion 99, where is re-actuated.Injection of fluid 96 is re-commenced, as shown in FIG. 5B, so thatfluid is again injected into said annular area so as to now be injectedinto an upwardly-extending adjacent fissure 5 a on a heel side of apenultimate fissure 5 b′, and producing oil which flows into saidproduction tubing via said penultimate fissure.

The above process is further repeated, as shown in FIG. 5C, andthereafter, successively converting injection fissures to productionfissures, always progressing in the direction of the heel 99 ofhorizontal portion 92, until the entirety of formation 6 has beenexposed to such process, and hydrocarbons recovered using such “drive”process.

Again, of course, the reverse of such process may similarly also beconducted, to achieve substantially the same result, progressivelydriving and recovering from formation 6, from a heel 99 to toe 100, andin effect reversing the sequence, as shown progressively in FIGS. 5C-5A.

In such embodiment, the fissures 5 a and 5 b, 5 b′, 5 b″, 5 b′″, 5 b^(iv) and 5 ^(v) are created as before, with fissure 5 a being thefissure most proximate the heel portion 99 (ie situated at the proximalend of horizontal portion 92), and fissures 5 b, 5 b′, 5 b″, 5 b′″, 5 b^(iv) and 5 ^(v) extending respectively toward the toe 100.

Production tubing 55, having actuable packer member 93 thereon and anopening 94 at a distal end thereof, is positioned in horizontal portion92 proximate heel portion 99. Packer 93 is actuated⁴ to create a sealbetween said tubing 55 and said wellbore 90, on a toe side of a mostproximal upwardly-extending fissure 5 a. Fluid 96 in into an annulararea intermediate said production tubing 55 and said wellbore 90 andthereby injected into said most proximal fissure 5 a, and producinghydrocarbons which drain into said wellbore via said remainingupwardly-extending fissure 5 b and which thereafter flow into saidproduction tubing 55 via said opening 94 therein. The process issuccessively repeated by de-actuating packer member 93 and moving saidpacker member 93 and production tubing 55 toward said toe portion 100,re-actuating said packer member 93 and re-instituting injection of saidfluid 96 into said annular area so as to inject said fluid 96 into apenultimate upwardly-extending fissure on a heel side of said mostproximal fissure 5 a, and producing oil which flows into said productiontubing via an adjacent remaining fissure. ⁴ In this embodiment packer 93is not actuated by pressure within tubing 55 but rather actuated viaother means well known to persons of skill in the art, such as byball-drop methods, which are not needed to be discussed herein.

The above process is further repeated, successively convertingproduction fissures to injection fissures, always progressing in thedirection of the toe 100 of horizontal portion 92, until the entirety offormation 6 has been exposed to such process, and hydrocarbons recoveredusing such “drive” process.

In another embodiment, the method of the present invention comprisesusing dual-tubing packers 12 a, 12 b and a single production/injectionwellbore 90 to achieve fluid injection in alternately spaced verticalfissures 5 a and further recovery of oil from alternately spacedrecovery fissures 5 b in the formation 6, and such alternative methodusing dual-tubing packers 12 a, 12 b is shown schematically in FIG. 12.

An enlarged view of the dual-tubing packers 12 a, 12 b used in thisparticular method is shown in FIG. 11.

As may be seen from FIG. 12, the method of the present invention forrecovering hydrocarbons from a subterranean formation 6 using fluidinjection in alternating hydraulic fractures 5 a, 5 b created information 6, using dual-tubing packers 12 a, 12 b, comprises the stepsof firstly drilling a single injection/production well 90 in formation6, having a vertical portion 91 and a lower horizontal portion 92extending horizontally outwardly from a lower end of said verticalportion 91.

Thereafter, in one embodiment of such method, a series of parallelupwardly-extending alternating fissures 5 a, 5 b respectively arecreated along the horizontal portion 92 of said injection/productionwell 90 by known fracking methods, such as inserting a series of packers9, to thereby create spaced-apart sections 7,8 of horizontal portion 92and allow supply of pressurized fracturing fluid to such isolatedsections 7,8 so as to create vertical upwardly-extending alternatingfissures 5 a, 5 b therefrom at spaced known distances along a length ofhorizontal portion 92 of injection/production wellbore 90.

Thereafter, if dual tubing packers 12 a, 12 b were used, such may thenbe re-used, or alternatively if they were not used, a dual tubing string10,11 having dual tubing packers 12 a, 12 b spaced therealong may beinserted in the horizontal wellbore 92 thereby placing a plurality ofpackers 12 a, 12 b each having dual tubing 10, 11 passing therethroughand coupled together by coupling male threads 13 on each of dual tubings10, 11 passing through packer 12 a coupled to and threadably inserted incouplings 14 on packer 12 b, and placing same along said length of saidhorizontal portion 92 of said injection/production well 90 andalternatingly spacing said packers 12 a, 12 b between saidupwardly-extending fissures 5 a, 5 b along said length as shown in FIG.12 thereby partitioning said length into alternatingly-spaced fluidinjection regions 7 and fluid recovery regions 8. One tubing 11 ofdual-tubing packers 12 a, 12 b has perforations 15 therein oppositealternatingly-spaced fissures 5 a in injection regions 7, and the otherof said dual tubing 10 having perforations 21 therein opposite remainingalternatingly-spaced fissures 5 b in recovery regions 8.

A pressurized fluid is then injected into one of said dual tubing,namely injection tubing 10 and thereby, via apertures 15 thereininjected into said fluid injection regions 7 and thus intoalternatingly-spaced fissures 5 a along said length of said horizontalportion of said injection/production well. Simultaneously, orsubsequently, hydrocarbons which drain into said alternatingly-spacedfluid recovery regions 8 via other alternatingly-spaced fissures 5 b andthereby into said other of said dual tubing 10 via apertures 21 thereinare pumped/produced to surface.

FIG. 13 shows a prior (unsatisfactory) oil recovery method (not thesubject of the present invention), wherein all fissures 5 b are used forproduction. Specifically, FIG. 13 is an enlarged schematicrepresentation of a portion of a formation 1 between two series offractures 5 b created along the length of the production wellbore 77,using only primary oil recovery, whereby collection is from allfissures/fractures 5 b. In such method, two (2) low-pressurepermeability production planes 75 are provided, wherein heated oil maydrain downwardly into production wellbore 77 for production to surface.Due to the lack of fluid drive, and in particular a fluid drive betweenadjacent alternatingly spaced fractures 5 b, only small fluid flowvectors 78, 79 are created for oil flowing into production fractures 5b. Disadvantageously, in “tight” formations a significant portion 1 a ofthe formation 1, namely the volume encircled by grey band “X”, continuesto possess trapped (unrecovered) bitumen which remains unrecovered bysuch process.

In comparison, FIG. 14 depicts a similar enlarged schematicrepresentation of a portion 1 a of a formation 1, using a method of oilrecovery of the present invention.

Specifically, FIG. 14 depicts a method where alternatingly-spacedinjection fractures 5 a and production fractures 5 b are positionedalong a length of a production wellbore 77. An injection plane 76,created from fluid such as diluents, heated steam, CO₂, orviscosity-reducing agents, is injected into injection fractures 5 a.Such fluid drives bitumen within the portion 1 a of formation 1 in thesingle direction of fluid flow vectors 78 namely towards productionfissures 5 b, which thereby forms a high permeability (low pressure)production plane 75 within reservoir 1 a, which allows bitumen to draindown into production wellbore 77 for production to surface.Advantageously, for “tight” formations, using such method of FIG. 14,and in contradistinction to the method of FIG. 13, bitumen is driven(swept) from substantially the entire volume of portion 1 a of formation1, and in particular from a larger volume of formation 1 than the volumeof the formation that is drained in FIG. 13, thus increasing efficiencyof production from a given volume of formation 1 as compared to themethod depicted in FIG. 13.

EXAMPLES

In order to demonstrate the efficacy of the methods of the presentinvention over the prior art, at least with respect to the firstvariation using two separate wells in comparison to the prior art, four(4) cases of numerical simulations were conducted using the ComputerModelling Group's STARS reservoir modeling software starting with astandard CMG model as modified, with the parameters of Table 1 below:

TABLE 1 Numerical simulation parameters Value Units ReservoirTemperature 73 Degree Celsius pressure 17,000 kPa Maximum safe injectionpressure 23,000 kPa Horizontal permeability 0.50 mD Verticalpermeability 0.05 mD Oil saturation 50 % Water saturation 50 % Fracturepermeability 2000 mD Oil density 45 Degree API Gas-oil-ratio 64Dissolved in oil Model Parameters Grid block size, l, j, k 1, 5, 1meters Number Grid blocks, l, j, k 200, 10, 40 number (1/4 element ofsymmetry) Full model volume 1.6E06 Cubic meters Bottom-hole pressure 100kPa

A generic “tight” reservoir light oil was assumed, and the modelemployed an element of symmetry representing ¼ of the affectedreservoir.

Test Results

FIGS. 9 & 10 show the oil production rates and Oil Recovery Factors,respectively, over time, for various embodiments of the presentinvention compared with the prior art “primary” recovery method usingproduction from all created fissures.

As regards FIG. 9, FIG. 9 shows the oil production rate for variousconfigurations as follows:

curve (a)—depicts oil production rate for the primary production methodusing production from each of the two wells drilled (i.e. from all ofthe fissures created in the formation) over time, over the period of 11years (i.e. 4015 days);

curve (b)—depicts oil production rate for the second embodiment of thepresent invention as a function of time (days), namely primaryproduction from all of the fissures created for a period of 2 years,followed by gas injection into every other fissure and production fromthe remaining fissures, over the remaining 9 years;

curve (c)—depicts oil production rate for the first embodiment of thepresent invention as a function of time (days), namely gas injectioninto every other fissure and production from the remaining fissures,over the period of 11 years; and

curve (d)—depicts oil production rate for the second embodiment of thepresent invention as a function of time (days), namely primaryproduction from all of the fissures created for a period of 2 years,followed by water injection into every other fissure and production fromthe remaining fissures, over the remaining 9 years.

As regards FIG. 10:

curve (a)—depicts oil % OOIP for the primary production method usingproduction from each of the two wells drilled (ie from all of thefissures created in the formation) over time, over the period of 11years (ie 4015 days);

curve (b)—depicts % OOIP for the second embodiment of the presentinvention as a function of time (days), namely primary production fromall of the fissures created for a period of 2 years, followed by gasinjection into every other fissure and production from the remainingfissures, over the remaining 9 years;

curve (c)—depicts % OOIP for the first embodiment of the presentinvention as a function of time (days), namely gas injection into everyother fissure and production from the remaining fissures, over theperiod of 11 years; and

curve (d)—depicts oil production rate for the second embodiment of thepresent invention as a function of time (days), namely production from ½the fissures, with remaining alternating fissures being injected withwater.

As may be seen from FIG. 9, the production rate of primary oilproduction [curve (a)] falls off very quickly. After 3-years theproduction rate [curve (a)] is only 2 m3/d with a Recovery Factor (fromFIG. 9) of 10.5%, which is an un-economical level. The 10-year RecoveryFactor (see FIG. 9) is only 13.3%.

However, if gas is injected in the manner of the present invention,namely in alternately spaced fractures, after 2 years of primary oilproduction, while keeping the injection pressure below the maximum safe(non-fracturing) level of 23,000 kPa, as may be seen from curve (c) ofFIG. 9, a surge of oil production occurs.

Table 2 below summarizes additional results from the above tests,including % OOIP obtained from FIG. 10 for arbitrary time periods of 3years and 11 years, with respect to four (4) different configurations,(i) “Primary”, meaning production from all fissures, without fluidinjection in alternate fissures; (ii) “Gas”, meaning production from ½the fissures, with remaining alternating fissures being injected withgas; (iii) “Primary then Gas” meaning initial production from allfissures, followed by production from ½ the fissures, with remainingalternating fissures being injected with gas; and (iv) “water”, meaningproduction from ½ the fissures, with remaining alternating fissuresbeing injected with water.

TABLE 2 Primary then Primary* Gas gas** water 3-year recovery factor,10.5 23.0 14.6 17.1 % OOIP 11-year recovery factor, 13.2 40.7 39.2 39.2% OOIP Cumulative gas rate — 60.3E06 48.8E06 — injected, S m3 Cumulativewater — — — 43,244 injected, m3 *Production from all fissures (Not partof this invention) **Two-years of primary production followed by 9-yearsof gas Injection.

When gas is injected from the outset [Curve (b)], instead of after 2years of primary oil production, the peak oil production rates occurapproximately 480 days (ie 1.3 years) earlier, which is beneficialregarding the value of money [compare curve (b) and curve (c)].Nevertheless, the delayed start to gas injection has only a modesteffect on the Oil Recovery factor, since after eleven years, as seenfrom FIG. 10 and Table 2, the difference in oil recovery factor (% OOIP)is relatively minor, namely only 1.5% [i.e. 40.7% for curve (b) ascompared with 39.2% for curve (c)].

Significantly, as seen from FIG. 10 and Table 2 above, using the fluiddrive oil recovery process of the present invention, in either the firstembodiment using immediate gas injection in the injection well fissuresand production from the production well fissures (namely curve (b) ofFIG. 8), or the second embodiment utilizing initial production from allfissures for a period of two years subsequently followed by injectionfrom the injection well and production from the production well [i.e.curve (c) of FIG. 8] after 11 years, each provide a high oil recoveryfactor of approximately 40%.

Conversely, again with reference to FIG. 10, with the prior art primaryproduction method comprising production from each of the production welland injection well, namely from all fissures created along two wells(i.e. curve (a) of FIG. 10), after 11 years such method merely producesan oil recovery factor of 13.2%.

Accordingly, in the scenario modelled, use of the present invention hasbeen able to increase the % OOIP recovery by an amount of approximately26% (i.e. 39.2%−13.2%).

The above disclosure represents embodiments of the invention recited inthe claims. In the preceding description, for purposes of explanation,numerous details are set forth in order to provide a thoroughunderstanding of the embodiments of the invention. However, it will beapparent that these and other specific details are not required to bespecified herein in order for a person of skill in the art to practicethe invention

The scope of the claims should not be limited by the preferredembodiments set forth in the foregoing examples, but should be given thebroadest interpretation consistent with the description as a whole, andthe claims are not to be limited to the preferred or exemplifiedembodiments of the invention.

1. A process for recovering hydrocarbons from a subterranean formationutilizing hydraulic fractures which become injection and productionchannels within said formation, comprising the steps of: (i) drilling aninjection well having a vertical portion and a horizontal portionextending horizontally outwardly from a lower end of said verticalportion; (ii) drilling a production well having a vertical portion and ahorizontal portion extending outwardly from a lower end of said verticalportion, wherein said horizontal portion of said production well issituated parallel to said horizontal portion of said injection well;(iii) fracturing the formation along each of said production well andinjection well and creating a plurality of upwardly-extending fissuresextending upwardly from, and situated along a length of, said horizontalportion of each of said injection well and said production well, saidupwardly-extending fissures created along said injection well mutuallyalternating along said horizontal length thereof with upwardly-extendingfractures situated along said production well; (iv) injecting apressurized fluid into said injection well and thereby into saidfissures above said injection well and thence into said formationthereby pressurizing said formation and causing said hydrocarbons withinsaid formation to be driven into said fissures above said productionwell, and to drain downwardly therein into said horizontal portion ofsaid production well; and (v) producing said hydrocarbons which collectin said horizontal portion of said production well to surface.
 2. Theprocess as claimed in claim 1, wherein said horizontal portion of saidinjection well is situated proximate to, but laterally spaced apartfrom, said horizontal portion of said production well.
 3. The method asclaimed in claim 1, wherein step (iii) comprising fracturing theformation comprises injecting a pressurized fluid into each of saidproduction well and injection well, at a plurality of discrete locationsalong a length of each of said horizontal portion of each of saidproduction well and injection well, wherein said discrete locations insaid production well substantially correspond in number to said discretelocations in said injection well and wherein said discrete locations andeach of said respective fissures extending upwardly along said injectionwell are in alternating linear spacing and substantially mutuallyadjacent relation with corresponding respective fissures extendingupwardly along said horizontal portion of said production well.
 4. Themethod as claimed in claim 3, further comprising the steps, after saidstep of injecting a pressurized fluid to fracture the formation, of:ceasing, for a time, injection of fluid into said injection well, andcollecting hydrocarbons which enter said fissures and which draindownwardly into said injection well and production well and producingsuch hydrocarbons to surface; upon production of hydrocarbons from theformation slowing to an unacceptable rate, continuing with steps(iv)-(v) of claim
 1. 5. The process for recovering hydrocarbons asclaimed in claim 1, wherein said pressurized fluid contains a proppant,or after said of fracturing the formation injecting a proppant underpressure into said created fissures, to render said fissures in apropped condition.
 6. The process for recovering hydrocarbons as claimedin claim 1: (i) wherein in said step of drilling said injection wellsaid horizontal portion extends horizontally outwardly from a lower endof said vertical portion along a lower portion of the formation; (ii)wherein in said step of drilling said production well said horizontalportion of said production well is situated proximate to, parallel with,and spaced apart from, said horizontal portion of said injection well;(iii) utilizing injection tubing, having therealong a plurality ofspaced-apart packer seals within a length of said horizontal portion ofsaid injection well, said injection tubing further having apertures orapertures which may be opened intermediate pairs of said spaced-apartpacker seals situated at locations at which said upwardly-extendingfractures are located along said injection well, and injecting saidpressurized fluid into said injection tubing and into said fissuresextending along said horizontal portion of said injection well; (iv)utilizing production tubing, having therealong a plurality ofspaced-apart packer seals similarly spaced apart as per said packerseals along said injection tubing, said production tubing further havingapertures, or apertures which may be opened, intermediate pairs of saidspaced-apart packer seals, along a length of said horizontal portion ofsaid production well, wherein said apertures in said production tubingare positioned in alternating and non-lateral alignment with saidapertures located in said injection tubing; (v) collecting from saidformation hydrocarbons in said production tubing which flow into saidfissures and which drain downwardly into said production tubing via saidapertures therein; and (vi) producing the hydrocarbons which collect insaid production tubing to surface.
 7. The process as claimed in claim 6,wherein: (a) step (i) further comprises the step of inserting andcementing a liner in the injection well; (b) and step (ii) furthercomprises the step of inserting and cementing a liner in said productionwell; (c) adding a step, after step (ii), of creating perforations insaid liner and cement in each of said horizontal portions of saidproduction and injection wells, at a plurality of discrete allocationstherealong, wherein said discrete locations in said production well areapproximately equal in number but linearly alternating with saidcorresponding perforations created in said liner in said injection well.8. A process for recovering hydrocarbons from a subterranean formationutilizing hydraulic fractures as alternating injection and productionchannels, respectively, comprising the steps of: (i) drilling aninjection well, having a vertical portion and a horizontal portionextending horizontally outwardly from a lower end of said verticalportion; (ii) inserting tubing, having therealong a plurality ofspaced-apart packer seals, within a length of said horizontal portion ofsaid injection well, said tubing further having apertures or apertureswhich may be opened intermediate pairs of said spaced-apart packerseals; (iii) drilling a production well proximate said injection well,having a vertical portion and a horizontal portion extending outwardlyfrom a lower end of said vertical portion, wherein said horizontalportion of said production well is situated proximate to, parallel with,and spaced apart from, said horizontal portion of said injection well;(iv) inserting tubing, having therealong a plurality of spaced-apartpacker seals similarly spaced apart as per said packer seals in saidinjection well, said tubing further having apertures, or apertures whichmay be opened, at locations intermediate pairs of said spaced-apartpacker seals, along a length of said horizontal portion of saidproduction well, wherein said apertures in said tubing in saidproduction well are positioned in non-lateral alignment with saidapertures in said injection well; (v) setting, if necessary, said packerseals in each of said respective horizontal portions of said injectionwell and said production well so as to prevent flow of fluid along anannular passage intermediate said tubing and said production well andinjection well, respectively; (vi) injecting into said injection well, afluid under pressure and causing said fluid to flow into said formationvia said apertures in said tubing therein, so as to create upwardlyextending fissures at each of said apertures along said injection well;(vii) injecting into said production well, a fluid under pressure andcausing said fluid to flow into said formation via said apertures insaid tubing therein, so as to create upwardly extending fissures at eachof said apertures along said production well; (viii) after step (vi)collecting, via said tubing in said horizontal portion of saidproduction well and said horizontal portion of said injection well, saidhydrocarbons which flow into said fissures and which drain downwardlyinto said tubing in said production well and said injection well; (ix)after a period of time and when production from said production well andsaid injection well decreases to an unsatisfactory rate, injecting afluid into said injection well and into said upwardly-extending fissuresalong said injection well; and (x) continuing to collect, via saidhorizontal portion of said production well, said hydrocarbons which flowinto said fissures above said production well and which drain downwardlyinto said tubing in said production well.
 9. The process as claimed inclaim 1, wherein the hydrocarbon is oil or gas.
 10. The process asclaimed in claim 1, wherein the hydrocarbon is methane and the fluid isCO2.
 11. The process as claimed in claim 1, wherein the fluid ismiscible or immiscible in the hydrocarbon.
 12. The process as claimed inclaim 1, wherein the fluid is a gas or a liquid.
 13. The process asclaimed in claim 1, wherein the fluid contains oxygen, for use in anin-situ combustion process.
 14. The process as claimed in claim 1,wherein the fluid comprises gases and/or liquids.
 15. The process asclaimed in claim 1, wherein gas and liquid are injected alternately ortogether into said fissures above said injection well.
 16. The processas claimed in claim 1, wherein said fluid is steam.
 17. A process forrecovering hydrocarbons from a subterranean formation utilizing fluidinjection in alternating fractures and producing from remainingalternatingly-spaced fractures, comprising the steps of: (i) drilling aninjection/production well, having a vertical portion and a horizontalportion extending horizontally outwardly from a lower end of saidvertical portion, said horizontal portion having a heel portionproximate said vertical portion, and a toe portion proximate a distalend of said horizontal portion; (ii) creating upwardly-extendingfissures in the formation along said horizontal portion by injecting apressurized fluid at a plurality of discrete spaced locations along alength of said horizontal portion; (iii) said pressurized fluidcontaining a proppant, or after step (ii) above injecting a proppantunder pressure into said created fissures, to render said fissures in apropped condition; and (iv) positioning injection tubing into saidwellbore, said injection tubing having an actuatable packer memberproximate a distal end of said tubing adapted when actuated to create aseal between said tubing and said wellbore, and situating such packermember and injection tubing within said wellbore on a heel side of amost distal upwardly-extending fissure; (v) injecting said pressurizedfluid, or injecting another fluid, into said injection tubing so as tocause said fluid to flow into said most distal upwardly-extendingfracture, and producing oil to surface which flows into an annular areain said wellbore via a penultimate fissure adjacent said most distalupwardly-extending fissure; (vi) deactivating said packer member andmoving said packer member and injection tubing toward said verticalportion, and re-instituting injection of said fluid so as to inject saidfluid into said penultimate upwardly-extending fissure, and producingoil which flows into said annular area via a fissure adjacent saidpenultimate fissure on a heel side of said penultimate fissure.
 18. Aprocess for recovering hydrocarbons from a subterranean formationutilizing fluid injection in alternating fractures and producing fromremaining alternatingly-spaced fractures, comprising the steps of: (i)drilling an injection/production well, having a vertical portion and ahorizontal portion extending horizontally outwardly from a lower end ofsaid vertical portion, said horizontal portion having a heel portionproximate said vertical portion, and a toe portion proximate a distalend of said horizontal portion; (ii) creating upwardly-extendingfissures in the formation along said horizontal portion by injecting apressurized fluid at a plurality of discrete spaced locations along alength of said horizontal portion; (iii)) said pressurized fluidcontaining a proppant, or after step (ii) above injecting a proppantunder pressure into said created fissures, to render said fissures in apropped condition; and (iv) positioning injection tubing into saidwellbore, said injection tubing having an actuatable packer memberproximate a distal end of said tubing adapted when actuated to create aseal between said tubing and said wellbore, and situating said packermember and injection tubing within said wellbore on a toe side of a mostproximal upwardly-extending fissure; (v) actuating said packer memberand injecting said pressurized fluid, or injecting another fluid, intosaid injection tubing so as to cause said fluid to flow into one or moreof remaining upwardly-extending fissures, and producing oil to surfacewhich flows into an annular area in said wellbore via said most proximalfissure; (vi) de-actuating said packer member and moving said packermember and injection tubing toward said toe portion, re-activating saidpacker member and re-instituting injection of said fluid, and injectingsaid fluid into remaining upwardly-extending fissures, and producing oilwhich flows into said annular area via said most proximal fissure and afurther adjacent penultimate fissure.
 19. A process for recoveringhydrocarbons from a subterranean formation utilizing fluid injection inalternating fractures and producing from remaining alternatingly-spacedfractures, comprising the steps of: (i) drilling an injection/productionwell, having a vertical portion and a horizontal portion extendinghorizontally outwardly from a lower end of said vertical portion, saidhorizontal portion having a heel portion proximate said verticalportion, and a toe portion proximate a distal end thereof; (ii) creatingupwardly-extending fissures in the formation along said horizontalportion by injecting a pressurized fluid at a plurality of discretespaced locations along a length of said horizontal portion; (iii) saidpressurized fluid containing a proppant, or after step (ii) aboveinjecting a proppant under pressure into said created fissures, torender said fissures in a propped condition; and (iv) positioningproduction tubing into said wellbore, said production tubing having anopening and an actuatable packer member thereon proximate a distal endthereof adapted when actuated to create a seal between said tubing andsaid wellbore, and situating said packer member proximate a toe portionof said wellbore on a heel side of a most distal upwardly-extendingfissure; (v) actuating said packer member and injecting said pressurizedfluid, or injecting another fluid, into an annular area intermediatesaid production tubing and said wellbore and thereby injecting saidfluid into a penultimate fissure adjacent said most distalupwardly-extending fissure, and producing hydrocarbons via saidproduction tubing which drain into said wellbore via said most distalupwardly-extending fissure and which thereafter flow into saidproduction tubing via said opening therein; (vi) deactuating said packermember and moving said packer member and production tubing toward saidheel portion, re-actuating said packer member and re-institutinginjection of said fluid into said annular area so as to inject saidfluid into an upwardly-extending adjacent fissure on a heel side of saidpenultimate fissure, and producing oil which flows into said productiontubing via said penultimate fissure.
 20. A process for recoveringhydrocarbons from a subterranean formation utilizing fluid injection inalternating fractures and producing from remaining alternatingly-spacedfractures, comprising the steps of: (i) drilling an injection/productionwell, having a vertical portion and a horizontal portion extendinghorizontally outwardly from a lower end of said vertical portion, saidhorizontal portion having a heel portion proximate said verticalportion, and a toe portion proximate a distal end thereof; (ii) creatingupwardly-extending fissures in the formation along said horizontalportion by injecting a pressurized fluid at a plurality of discretespaced locations along a length of said horizontal portion; (iii) saidpressurized fluid containing a proppant, or after step (ii) aboveinjecting a proppant under pressure into said created fissures to rendersaid fissures in a propped condition; and (iv) positioning productiontubing in said wellbore, said production tubing having an opening and anactuatable packer member thereon proximate a distal end thereof adaptedwhen actuated to create a seal between said tubing and said wellbore,and situating said packer member proximate a heel portion of saidwellbore on a toe side of a most proximal upwardly-extending fissure;(v) actuating said packer member and injecting said pressurized fluid,or injecting another fluid, into an annular area intermediate saidproduction tubing and said wellbore and thereby injecting said fluidinto said most proximal fissure adjacent, and producing hydrocarbons viasaid production tubing which drain into said wellbore via said remainingupwardly-extending fissure and which thereafter flow into saidproduction tubing via said opening therein; and (vi) deactuating saidpacker member and moving said packer member and production tubing towardsaid toe portion, re-actuating said packer member and re-institutinginjection of said fluid into said annular area so as to inject saidfluid into a penultimate upwardly-extending fissure on a heel side ofsaid most proximal fissure, and producing oil which flows into saidproduction tubing via an adjacent remaining fissure.
 21. A method forrecovering hydrocarbons from a subterranean formation using fluidinjection in alternating fractures and producing from remainingalternatingly-spaced fractures, using dual-tubing packers, comprisingthe steps of: (i) drilling a single injection/production well in saidformation, having a vertical portion and a lower horizontal portionextending horizontally outwardly from a lower end of said verticalportion; (ii) fracturing the formation along said horizontal portion ofsaid injection/production well and creating a plurality ofupwardly-extending fissures extending upwardly from, and situated alonga length of, said horizontal portion; (iii) placing a plurality ofpackers each having dual tubing therein along said length of saidhorizontal portion of said injection/production well and alternatinglyspacing said packers between said upwardly-extending fissures along saidlength thereby partitioning said length into alternatingly-spaced fluidinjection regions and fluid recovery regions, one of said dual tubinghaving perforations therein opposite alternatingly-spaced fissures andthe other of said dual tubing having perforations therein oppositeremaining alternatingly-spaced fissures; (iv) injecting a pressurizedfluid into one of said dual tubing and thereby injecting pressurizedfluid into said fluid injection regions and thus intoalternatingly-spaced fissures along said length of said horizontalportion of said injection/production well; and (v) producing saidhydrocarbons which drain into said alternatingly-spaced fluid recoveryregions via other alternatingly-spaced fissures from said other of saiddual tubing.
 22. The process as claimed in claim 8, wherein thehydrocarbon is oil or gas.
 23. The process as claimed in claim 8,wherein the hydrocarbon is methane and the fluid is CO2.
 24. The processas claimed in claim 8, wherein the fluid is miscible or immiscible inthe hydrocarbon.
 25. The process as claimed in claim 8, wherein thefluid is a gas or a liquid.
 26. The process as claimed in claim 8,wherein the fluid comprises gases and/or liquids.
 27. The process asclaimed in claim 8, wherein gas and liquid are injected alternately ortogether into said fissures above said injection well.
 28. The processas claimed in claim 8, wherein said fluid is steam.